Concept Guide

For bridge protocol data units (BPDU) ltering behavior, refer to Removing an Interface from the Spanning Tree Group.
Modifying Global Parameters
You can modify RSTP parameters.
The root bridge sets the values for forward-delay, hello-time, and max-age and overwrites the values set on other bridges participating in
the Rapid Spanning Tree group.
• Forward-delay — the amount of time an interface waits in the Listening state and the Learning state before it transitions to the
Forwarding state.
• Hello-time — the time interval in which the bridge sends RSTP BPDUs.
• Max-age — the length of time the bridge maintains conguration information before it refreshes that information by recomputing the
RST topology.
NOTE: Dell Networking recommends that only experienced network administrators change the Rapid Spanning Tree group
parameters. Poorly planned modication of the RSTP parameters can negatively aect network performance.
The following table displays the default values for RSTP.
Table 65. RSTP Default Values
RSTP Parameter Default Value
Forward Delay 15 seconds
Hello Time 2 seconds
Max Age 20 seconds
Port Cost:
• 10-Gigabit Ethernet interfaces
• 40-Gigabit Ethernet interfaces
• Port Channel with two 40-Gigabit Ethernet interfaces
• Port Channel with two 10-Gigabit Ethernet interfaces
Port Cost:
• 1400
• 2000
• 600
• 1800
Port Priority 128
To change these parameters, use the following commands.
• Change the forward-delay parameter.
PROTOCOL SPANNING TREE RSTP mode
forward-delay seconds
The range is from 4 to 30.
The default is 15 seconds.
• Change the hello-time parameter.
PROTOCOL SPANNING TREE RSTP mode
hello-time seconds
NOTE
: With large congurations (especially those congurations with more ports) Dell Networking recommends
increasing the hello-time.
The range is from 1 to 10.
The default is 2 seconds.
• Change the max-age parameter.
Rapid Spanning Tree Protocol (RSTP)
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